The present invention relates to an adaptive cruise control (ATCC) system which executes a following control for following a preceding vehicle ahead of a host-vehicle while keeping a predetermined inter-vehicle distance, and more particularly to an ATCC system which cancels the following control for keeping the inter-vehicle distance when a host-vehicle speed becomes smaller than a control-cancel vehicle speed.
Japanese Patent Provisional Publication No. 2000-313245 discloses a following control system which cancels a following control by decreasing a deceleration of a host-vehicle according to elapsed time.
However, this control system is arranged to decrease a deceleration according to the elapse of time with a predetermined constant gradient when the host-vehicle speed becomes lower than a preset vehicle speed. This arrangement varies a control-cancel vehicle speed according to the magnitude of the deceleration, and therefore a driver of the host-vehicle may receive a strange feeling therefrom.
It is therefore an object of the present invention to provide an improved adaptive cruise control (ATC) system which enables a deceleration at a predetermined control-cancel vehicle speed to be smoothly controlled at a value near zero regardless a magnitude of the deceleration when the deceleration is gradually decreased from a moment that the host-vehicle speed reaches the following control-cancel vehicle speed.
An aspect of the present invention resides an adaptive cruise control (ATCC) system for a host-vehicle which system comprises a controller. The controller is programmed to detect an inter-vehicle distance between the host-vehicle and a preceding vehicle ahead of the host-vehicle, to detect a host-vehicle speed of the host-vehicle, to calculate a command vehicle speed on the basis of the inter-vehicle distance and the host-vehicle speed to bring the inter-vehicle distance closer to a target inter-vehicle distance, to control one of a driving force and a braking force according to the command vehicle speed, to cancel controlling one of the driving force and the braking force according to the command vehicle speed when the host-vehicle speed is lower than or equal to a control-cancel vehicle speed, and to gradually decrease a deceleration of the host-vehicle according to an approach of the host-vehicle speed toward the control-cancel vehicle speed when the host-vehicle speed becomes lower than or equal to a gradual-deceleration starting vehicle speed during a period of decreasing the host-vehicle vehicle toward the control-cancel vehicle speed, so that the deceleration takes a value near zero when the host-vehicle speed reaches the control-cancel vehicle speed.
Another aspect of the present invention resides in an adaptive cruise control (ATCC) system for a host-vehicle which system comprises a controller. The controller is programmed to detect an inter-vehicle distance between the host-vehicle and a preceding vehicle ahead of the host-vehicle, to detect a host-vehicle speed of the host-vehicle, to calculate a command vehicle speed on the basis of the inter-vehicle distance and the host-vehicle speed to bring the inter-vehicle distance closer to a target inter-vehicle distance, to control one of a driving force and a brake hydraulic pressure according to the command vehicle speed, to cancel controlling one of the driving force and the brake hydraulic pressure according to the command vehicle speed when the host-vehicle speed is lower than or equal to a control-cancel vehicle speed, and to gradually decrease the brake hydraulic pressure according to an approach of the host-vehicle speed toward the control-cancel vehicle speed when the host-vehicle speed becomes lower than or equal to a gradual-deceleration starting vehicle speed during a period of decreasing the host-vehicle speed toward the control-cancel vehicle speed, so that the brake hydraulic pressure takes a value near zero when the host-vehicle speed reaches the control-cancel vehicle speed.
A further another aspect of the present invention resides in a method of executing an adaptive cruise control of a host-vehicle. The method comprises a step of detecting an inter-vehicle distance between the host-vehicle and a preceding vehicle ahead of the host-vehicle; a step of detecting a vehicle speed of the host-vehicle; a step of calculating a command vehicle speed on the basis of the inter-vehicle distance and the host-vehicle speed to bring the inter-vehicle distance closer to a target inter-vehicle distance; a step of controlling one of a driving force and a braking force according to the command vehicle speed; a step of canceling to control one of a driving force and a braking force according to the command vehicle speed when the host-vehicle speed is smaller than or equal to a control-cancel vehicle speed; and a step of gradually decreasing a deceleration of the host-vehicle according to an approach of the host-vehicle speed to the control-cancel vehicle speed when the host-vehicle speed becomes lower than or equal to a gradual-deceleration starting vehicle speed during a period of decreasing the host-vehicle speed toward the control-cancel vehicle speed, so that the deceleration takes a value near zero when the host-vehicle speed reaches the control-cancel vehicle speed.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.